How much income will that 401(k) generate?

The retirement savings industry wants you to instead think about the monthly paycheck the account can generate. In other words, the thinking goes, consider it more like a pension.

BlackRock Inc., for example, rolled out a series of indexes about a year ago that aim to track the cost of future retirement income.

The estimates are based on measures including future inflation, the cost of annuities and life expectancy.

This month, the company said the amount of money required to generate that income rose, largely because of declining interest rates.

For a 55-year-old with about $264,000 in retirement savings, for example, the company said the "cost" of providing $18,719 in annual retirement income rose 7.15 percent from June 2013 to June 2014. (In other words, generating that same amount of income would require higher contributions or higher investment earnings.)

"We demonstrated that the actual cost of retirement income fluctuates quite a bit," particularly for younger savers, said Chip Castille, a BlackRock managing director who leads its U.S. Retirement Group.

Declining rates also meant that for a hypothetical 64-year-old with savings of about $251,000, the cost of funding an annual retirement paycheck of $12,582 rose by about 4 percent.

Rising rates or other factors largely out of the control of individuals, of course, could drive costs lower.

So what's the point of tracking all this?

BlackRock, for one, wants to use the language of monthly income to drive 401(k) savers toward investment products that use more pensionlike characteristics, a process known as liability-driven investing.

The company is offering fixed-income portfolios for sponsors of 401(k) plans that include this technique.

For a broader retirement audience, though, the mantra is aimed at getting consumers to think about how they'll live year to year, or month to month, on what they've saved.

There's just one hitch: Making 401(k) balances look more like monthly pension statements runs the risk, some experts and even plan sponsors fear, of lulling savers into thinking those monthly income projections are actually something they can count on from their employers.

Employers are scared to express 401(k) balances in income terms because "they don't want it to be perceived as a guarantee," said Jeffrey Brown, a finance professor at the University of Illinois.

Despite the concern, Brown supports the idea of expressing monthly income measures on 401(k) statements, as well as new Treasury Department rules announced this month that make it easier for plans to offer deferred annuities. (Brown sits on the board of TIAA-CREF, a provider of annuities.)

"Even if the estimates are imperfect, it's still better than what consumers have now, which is nothing, and consumers are notoriously bad about making that conversion" from a lump sum to monthly income, Brown said.

Interestingly, BlackRock found that 55-year-olds at the median income and retirement savings levels, according to data from the Employee Benefit Research Institute, are on track to replace 69 percent of pre-retirement income.

By contrast, the median savings in the 64-year-old group would only replace about 59 percent of pre-retirement income, the company said.

"The reality for investors is that you can't plan your future if you don't know where you are today," said Robert Fairbairn, global head of BlackRock's retail and iShares businesses.